Process for burning different sized particulate material in a pulverized fuel burner



Jan. 18, 1966 E. J. WASP 3,229,651

PROCESS FOR BURNING DIFFERENT SIZED PARTIGULATE MATERIAL IN A PULVERIZED FUEL BURNER Filed June 6, 1962 2 Sheets-Sheet 1 BOILER K32 BURNER FIG.

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ATTORNEY E. J. WASP 3,229,651 PROCESS FOR BURNING DIFFERENT SIZED PARTICULATE Jan. 18, 1966 MATERIAL IN A PULVERIZED FUEL BURNER Flled June 6, 1962 2 Sheets-Sheet 2 Tuzmnm 3.

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E J. WASP N dim ATTORNEY United States Patent 3,229,651 PROCESS FOR BURNHNG DHFFERENT SIZED PAR- TICULATE MATERIAL IN A PULVERIZED FUEL BURNER Edward J. Wasp, Pittsburgh, Pa., assignor to Consolidation Coal Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed .Iune 6, 1962, Ser. No. 200,548 7 Claims. (Cl. 1107) This is a continuation-in-part of my forfeited copending US. patent application Serial No. 84,684, filed January 24, 1961, and entitled, Process for Burning Different Sized Particulate Material in a Pulverized Fuel Burner.

This invention relates to a process for burning particulate solid carbonaceous material of various sizes in a pulverized fuel burner and more particularly to a process for efiiciently reducing the size of large particles of coal suspended in a coal-water slurry to provide a suitable feed for a pulverized fuel burner.

In US. Patent No. 2,791,471, entitled, Transportation of Coal by Pipeline; copending application Serial No. 9,884, filed February 19, 1960, entitled, Preparing Coal for Transportation by Pipeline, now abandoned; and in copending US. patent application Serial No. 134,631, filed August 29, 1961, entitled, Transportation of Coal by Pipeline, now Patent No. 3,168,350, each of which are assigned to the assignee of this document, there are described methods of transporting coal particles of various sizes as an aqueous slurry over long distances through a pipeline. These new methods of transporting coal directly from the mine to the power plant or power generating station have materially contributed to the position of coal in the field of power generation. For example, the commercial pipeline extending a distance of 108 miles between a mine in southern Ohio and a power generating station along the shore of Lake Erie has transported several million tons of coal as an aqueous slurry at substantial savings in transportation costs.

One of the major cost factors in this new method of transporting coal is the processing of the slurry at the power station to separate the coal from the water. In the past, conventional means such as filters, thermal driers, thickeners and the like have been employed to remove substantially all of the water from the coal. The coal was then stored at the combustion terminal in its dry state, and was fed to the combustion units in a known conventional manner.

The storage and transportation of the dried coal within the combustion terminal presents the well-known problems of dust and explosion hazards. Expensive equipment must be provided to minimize these hazards. Another problem exists in metering the amount of coal fed to the burner. Elaborate metering means are required to deliver the proper predetermined amounts of coal to the fuel burner. A highly desirable solution to the above material handling problems in the combustion terminal would be to supply the coal in such a state that it can be stored as a liquid similar to the petroleum fuels literally a liquid fuel. The liquid fuel could then be fed by inexpensive, accurate metering means from a tank-type storage means directly to the fuel burner. A liquid fuel of this type would eliminate the expensive equipment employed in dewatering, drying, storing and conveying the dried coal to the fuel burner.

In copending application Serial No. 9,884 a slurry having highly desirable storage and flow properties is described. This slurry, which hereinafter will be called a stabilized slurry, retains the coal particles suspended therein under static conditions. It is now possible with "ice the stabilized coal-water slurry of the type described in copending application Serial No. 9,884 to store the slurry in a tank-type storage means under quiescent conditions for substantial periods of time.

A means has also been discovered for increasing the coal concentration in the slurry within the combustion terminal to a degree that the slurry can be fed directly to certain types of fuel burners without additional dewatering. It is now possible with the stabilized slurry to have all the desirable advantages of a liquid fuel. The stabilized slurry can be transported within the combustion terminal by pumping the stabilized slurry through conventional conduits by means of energy supplied by conventional pumping means. Handling of the coal particles in this manner within the combustion terminal eliminates the dust and explosion hazards and further minimizes the equipment required to process the coal particles in the slurry prior to combustion.

There are several critical relationships upon which both the dynamic and static stabilities of the heretofore described stabilized slurry depend. For example, to obtain a minimum pressure drop while being transported through a long-distance pipeline, it is highly desirable to have about 10 percent of the coal particles of a size that will be retained on a 14 mesh Tyler Standard screen. The fraction that passes through a 14 mesh Tyler Standard screen and is retained on a 200 mesh Tyler Standard screen should be about 60 percent. The remaining 30 percent of the coal particles pass through a 200 mesh Tyler Standard screen. It has also been found that the stabilized slurry should have a coal concentration of about 60 percent by weight to obtain the desired minimum pressure drop while being transported through the longdistance pipeline. The above factors, therefore, dictate from an economic aspect the size of the coal particles delivered to the combustion terminal.

In certain existing installations where pulverized fuel burners are employed, substantially complete combustion of the coal particles occurs when at least 60 percent of the coal particles are of a size that will pass through a 200 mesh Tyler Standard screen. Therefore, in such existing installations or installations where pulverized fuel burners having this particle size requisite are employed, any coal slurry, whether stabilized or not, that is to be burned in the pulverized fuel burners should be processed to reduce the size of the coal particles to the desired size.

It remains highly desirable, however, to provide a combustion terminal wherein the coal particles may be stored as a liquid to minimize dust and explosion hazards. Further, the transportation of the coal to the burner should, if possible, be effected through closed conduits either as a liquid or a pneumatic suspension.

According to one embodiment of my invention, a portion of the water in the slurry is vaporized to form a dispersion of the coal particles in the water vapor. The dispersion is transported pneumatically through a conduit to a cyclone separating means where the particles too large for complete combustion in a pulverized fuel burner are separated from the dispersion. These separated particles are transported through a conduit to a pulven'zer where the separated particles are comminuted to a size suitable for complete combustion in a pulverized fuel burner. These comminuted particles are then transported pneumatically to the pulverized fuel burner. The dispersion of fine-coal particles suitable for economic combustion in a pulverized fuel burner and the water vapor are transported pneumatically from the cyclone separating means to the pulverized fuel burner. In this manner, the large coal particles in the slurry are reduced in size so that there is substantially complete combustion of all the coal particles that enter the pulverized fuel burner.

According to another embodiment of my invention, a portion of the water in the stabilized slurry is vaporized to form a dispersion of the coal particles in the water vapor. The dispersion is transported pneumatically through a conduit to a cyclone separating means where the particles too large for complete combustion in a pulverized fuel burner are separated from the dispersion. The large particles so separated are conveyed to a mixing device where the large particles are mixed with a portion of the stabilized slurry to provide a mixture having a predetermined Water content. This mixture is conveyed from the mixing means to a pulverizer where the particles in the mixture that are too large for economic combustion in a pulverized fuel burner are comminuted to a suitable size. The mixture is then transported through a conduit from the pulverizer to the pulverized fuel burner. The dispersion of fine coal particles suitable for economic combustion in a pulverized fuel burner and the water vapor are transported pneumatically from the cyclone separating means to the pulverized fuel burner. In this manner, the large particles in the stabilized slurry are reduced in size so that there is substantially complete combustion of all the coal particles in the pulverized fuel burner.

The described processes provide efficient separation of the finer coal particles from the larger coal particles in the cyclone separator. The liquid content of the dispersion is reduced to a point where the cyclone separator operates efficiently and there is a minimum agglomeration of coal particles therein.

Accordingly, the principal object of this invention is to provide methods for burning different sized coal particles of a coal-water slurry in a conventional fuel burner.

Another object of this invention is to provide a means for separating the finer sized coal particles from a coalwater slurry and introducing the finer coal particles into a pulverized fuel burner.

A further object of this invention is to provide processes for separating the larger sized particles from a coal- Water slurry and comminuting the larger sized coal particles into a size that is suitable for efficient combustion in a pulverized fuel burner.

These and other objects of this invention will become apparent from the following description when read in conjunction with the attached drawings.

In the drawings:

FIGURE 1 is a schematic illustration of the combustion terminal arranged to burn different sized coal particles contained in stabilized coal-water slurry in a conventional pulverized fuel burner.

FIGURE 2 is a schematic illustration of another combustion terminal similar to that of FIGURE 1.

Referring to FIGURE 1, a stabilized coal-water slurry having a concentration of from 50 to 70 percent by weight coal and the remainder water is transported through a pipeline from a distant mine and is deposited in a tank-type storage means 12. The size consist of the coal particles in the stabilized slurry is such that about 10 percent by weight of the particles will be retained on a 14 mesh Tyler Standard screen; about 60 percent by weight of the coal particles will pass through a 14 mesh Tyler Standard screen and be retained on a 200 mesh Tyler Standard screen; and the remaining 30 percent by weight of the coal particles will pass through a 200 mesh Tyler Standard screen.

The stabilized slurry is maintained in the storage means 12 until required for combustion. When so required, the slurry is withdrawn from the storage tank 12 and is introduced into a pump 14 which transports the slurry through conduit 16 to a vaporizing means 18. The vaporizing means 18 may be a conventional thermal drier or any means operable to vaporize a portion of the liquid in the slurry. Flue gas and air at a temperature of about 700 F. may be introduced into the vaporizing means 18 through conduit 20. The flue gas at this elevated temperature may be obtained from conventional sources such as the combustion unit or boiler. A sufiicient volume of flue gas and air at this elevated temperature is introduced into the vaporizing means 18 to vaporize a substantial portion of the water present in the slurry and form a dispersion of coal particles in the water vapor and flue gas. For example between 23 and 48 percent by weight of the slurry introduced into the vaporizing means, depending upon the coal concentration, is vaporized so that the liquid moisture content of the coal in the dispersion is between 5 and 10 percent by weight. The liquid water remaining in the dispersion appears as surface moisture on the coal particles and is insufiicient to cause agglomeration of the coal particles in the dispersion.

The dispersion leaves the vaporizing means 18 through the conduit 22. A suflicient volume of gas and air is introduced into the vaporizing means 18 to provide a pneumatic conveying means for the dispersion through conduit 22. The dispersion conveyed through conduit 22 is introduced into a cyclone separator 24. The velocity of the dispersion is controlled so that as it is introduced into cyclone separator 24 the coal particles which will remain on a 200 mesh Tyler Standard screen are separated from the dispersion and are withdrawn from the cyclone separator 24 by means of gravity through stand leg 26. The particles withdrawn through stand leg 26 will hereinafter be termed the coarse or large particles.

The large particles are introduced into a comminuting means 28 which may be a conventional pulverizer or the like. The large particles are reduced in size within comminuting means 28 so that they will be suitable for economic combustion in a pulverized fuel burner. The comminuted particles are subjected to an air stream within the comminuting means 28 and are conveyed from comminuting means 28 through conduit 30 to a pulverized fuel burner 32. Conduit 34 pneumatically conveys the dispersion of fine coal and water vapor from the cyclone separator 24 to the same pulverized fuel burner 32. Thus the coal particles of the dispersion conveyed through conduit 34 and the comminuted coal particles conveyed through conduit 30 are transported pneumatically to the pulverized fuel burner 32.

An example of the process hereinbefore described is as follows.

A stabilized coal-water slurry having a concentration of about 70 percent coal by weight and the remainder water is introduced into vaporizing means 18. The size of the coal particles in the stabilized slurry is such that about 70 percent of the coal particles will remain on a 200 mesh Tyler Standard screen and the remaining 30 percent of the particles will pass through a 200 mesh Tyler Standard screen. A predetermined volume of flue gas and air is introduced into the vaporizing means 18 and vaporizes between 23 and 26.5 percent by weight of the slurry to form a dispersion of water vapor, flue gas, and coal particles having 5 to 10 percent by weight liquid water on their surface. This dispersion is conveyed pneumatically to the cyclone separator 24. Substantially all of the coal particles which will remain on a 200 mesh Tyler Standard screen are separated from the dispersion in the cyclone separator and enter conduit 26. These particles are comminuted within comminuting means 28 so that substantially all of the comminuted particles will pass through a 200 mesh Tyler Standard screen and are thereby suitable for combustion in a conventional pulverized fuel burner. The comminuted particles from comminuting means 28 and the dispersion from the cyclone separator 24 are conveyed to a pulverized fuel burner for combustion therein.

Referring to FIGURE 2, a second combustion terminal is shown schematically. A stablized coal-water slurry having a concentration of about 60 percent by weight coal and 40 percent by weight liquid water is transported through a pipeline 110 from a distant mine and is deposited in a tank-type storage means 112. The size consist of the coal particles in the stabilized slurry is such that about percent by weight of the particles have a size which will be retained on a 14 mesh Tyler Standard screen. About 60 percent by weight of the coal particles have a size which will pass through a 14 mesh Tyler Standard screen and be retained on a 200 mesh Tyler Standard screen. The remaining 30 percent by weight of the coal particles are of a size which will pass through a 200 mesh Tyler Standard screen.

The stabilized slurry is maintained under substantially quiescent conditions in the storage means 112 until required for combustion. The slurry withdrawn from the storage tank 112 is introduced into a pump 114 which transports the slurry through conduit 116 to a vaporizing means 118. The vaporizing means 118 may be a conventional thermal drier or any means operable to vaporize a portion of the liquid in the slurry. Flue gas and air at a temperature of about 700 F. may be introduced into the vaporizing means 118 through conduit 120. The flue gas at this elevated temperature may be obtained from conventional sources such as the combustion unit or boiler. A sufiicient volume of flue gas and air at this elevated temperature is introduced into the vaporizing means 118 to vaporize a substantial portion of the Water present in the slurry and form a dispersion of coal particles in the water vapor and flue gas. For example, between 34-37 percent by weight of the slurry introduced into the vaporizing means 118 is vaporized so that the liquid moisture content of the coal in the dispersion is between 5-10 percent by weight. The remaining liquid water in the dispersion appears as surface moisture on the coal particles and is insufiicient to cause agglomeration of the coal particles in the dispersion.

The dispersion leaves the vaporizing means 118 through the conduit 122. A suflicient volume of gas and air is introduced into the vaporizing means 118 to provide a pneumatic conveying means for the dispersion through conduit 122. The dispersion conveyed through conduit 122 is introduced into a cyclone separator 124. The velocity of the dispersion is controlled so that as it is introduced into cyclone separator 124, the coal particles having a size which will remain on a 200 mesh Tyler Standard screen are separated from the dispersion and are withdrawn from the cyclone separator 124 by means of gravity through stand leg 126. The particles withdrawn through stand leg 126 will hereinafter be termed the coarse or large particles.

The large coal particles separated from the dispersion are introduced through stand leg 126 into a mixing means 128 which may be any conventional mixing device. A rotary seal type valve 127 regulates the rate of withdrawal of the particles from stand leg 126. The large coal particles entering the mixing device 128 have a liquid moisture content of between about 5-10 percent by weight which adheres to the particles as a surface moisture. A portion of the slurry discharged from pump 114 is conveyed through conduit 116 to conduit 130 and through conduit 130 to mixing device 128. Valves 132 and 134 proportion the amount of slurry entering vaporizing means 118 and the mixing means 128.

The amount of slurry entering mixing means 128 is so regulated that the large coal particles entering mixing means 128 through stand leg 126 and the stabilized slurry entering through conduit 130 provide a mixture of coal particles and water wherein the concentration of liquid water is about 18 percent by weight. The mixture is withdrawn from mixing means 128 and is transported through conduit 136 to a comminuting means 138 which may be a conventional pulverizer or the like. The larger particles in the mixture which are unsuitable for economic combustion in a pulverized fuel burner are reduced in size to a size suitable for economic combustion in the pulverized fuel burner. The mixture is subjected to heated air within the pulverizer 138 and is conveyed from pulverizer 138 through conduit 140 to a pulverized fuel burner 144. Conduit 142 pneumatically conveys the dispersion from the cyclone separator 124 to the same pulverized fuel burner 144. Thus the coal particles of the dispersion conveyed through conduit 142 and the coal particles of the mixture conveyed through conduit 140 are transported pneumatically to the pulverized fuel burner 144.

In this manner a stabilized coal-water slurry having certain coal particles unsuitable because of size for economic combustion in a pulverized fuel burner is treated so that all the particles are reduced to a size suitable for economic combustion in a conventional pulverized fuel burner. The reduction in size of the larger coal particles and the transportation of the coal particles from the storage means to the fuel burner is accomplished without conventional mechanical means and the coal particles are not subjected to dust and explosion hazards. With the heretofore described process, the coal particles in the stabilized slurry are subjected to combustion in a pulverized fuel burner without mechanical separation of the Water from the slurry.

An example of the process of FIGURE 2 is as follows.

A stabilized coal-Water slurry having a concentration of about 60 percent coal by weight and the remainder Water is introduced into vaporizing means 118. The size of the coal particles in the stabilized slurry is such that about 70 percent byweight of the coal particles are of a size which will remain on a 200 mesh Tyler Standard screen. The remaining 30 percent by weight of the particles are of a size which will pass through a 200 mesh Tyler Standard screen. A predetermined volume of flue gas and air is introduced into the vaporizing means 118 and vaporizes between 34-37 percent by weight of the slurry to form a dispersion of water vapor, flue gas, and coal particles having 5-10 percent by Weight liquid water on their surfaces. The dispersion is conveyed pneumatically to the cyclone separator 124. Substantially all of the coal particles having a size which will remain on a 200 mesh Tyler Standard screen are separated from the dispersion in the cyclone separator and enter conduit 126. The larger coal particles having a surface moisture of between 5-10 percent by weight are mixed with a portion of the stabilized coal-water slurry having about a 40 percent by weight liquid water content to provide a mixture having about 18 percent water by weight. The mixture is introduced into a conventional pulverizer 138 and the coal particles in the mixture are comminuted so that substantially all of the particles will pass through a 200 mesh Tyler Standard screen and are thereby suitable for combustion in a conventional pulverized fuel burner. The mixture from the pulverizer 138 and the dispersion from the cyclone separator 124 are conveyed to a pulverized fuel burner for combustion therein.

According to the provision of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

Iclaim:

1. A process for burning the different sized coal particles of a coal-water slurry in a pulverized fuel burner, certain of said coal particles in said slurry having a size greater than a predetermined size, said process comprising subjecting said slurry to a gas at an elevated temperature to vaporize a portion of said water in said slurry to form a suspension of said different sized coal particles in said gas, separating said coal particles having a size greater than a predetermined size from said suspension, mixing said separated coal particles with a portion of said slurry to provide a coal-water mixture having a predetermined concentration of coal by weight, =comminuting at least a portion of said coal particles having a size greater than a predetermined size in said mixture to a size less than said predetermined size, burning said coal particles in said suspension and in said mixture in a pulverized fuel burner.

2. A process for burning the ditferent sized coal particles of a coal-water slurry in a pulverized fuel burner, about 70 percent by Weight of the coal particles in said slurry having a size which will be retained on a 200 mesh Tyler Standard screen, said process comprising subjecting said slurry to a gas at an elevated temperature to vaporize a portion of said water in said slurry to form a sus ension of said different sized coal particles in said gas, said suspension containing coal particles having between and 10 percent liquid water by weight on their surfaces, separating in a cyclone separator substantially all of said coal particles having a size that is retained on a 200 mesh Tyler Standard screen from said suspension, mixing said separated coal particles with a portion of said slurry to form a mixture having about 18 percent water by weight, comminuting at least a portion of said coal particles in said mixture so that substantially all of said particles will pass through a 200 mesh Tyler Standard screen and burning said coal particles in said suspension and in said comminuted mixture in a pulverized fuel burner.

3. A process for burning the coal particles of a coalwater slurry in a pulverized fuel burner, said coal particles having a spectrum of sizes and about 70 percent by weight of said particles having a s ze which will be retained on a 200 mesh Tyler Standard screen, said slurry having a coal concentration of about 60 percent by weight and the remainder Water, said process comprising introducing a first portion of said slurry into a vaporizing means, introducing a gas at an elevated temperature into said vaporizing means, vaporizing between 34 to 37 percent by Weight of said slurry and forming a dispersion of coal particles in a vapor, introducing said dispersion into a cyclone separator, separating substantially all of said coal particles having a size which will be retained on a 200 mesh Tyler Standard screen from said dispersion, introducing said separated particles into a mixing means, introducing a second portion of said slurry into said mixing means and forming a mixture having about 18 percent water by weight and the remainder coal particles, introducing said mixture into a comminuting means, comminuting certain of said coal particles in said mixture so that substantially all of said coal particles Will pass through a 200 mesh Tyler Standard screen and introducing said dispersion and said comminuted mixture into a pulverized fuel burner for combustion therein.

4. A process for burning the different sized coal particles of a stabilized coal-water slurry in a pulverized fuel burner, certain of said coal particles in said stabilized slurry having a size greater than a predetermined size, said process comprising maintaining an inventory of stabilized slurry in a storage means under substantially quiescent conditions, withdrawing .a first stream of said stabilized slurry from said storage means, transporting by pumping through an enclosed conduit said first stream of slurry from said storage means to a vaporizing means, subjecting said slurry in said vaporizing means to a gas at an elevated temperature to thereby vaporize a portion of said water in said stabilized slurry to form a suspension of said different sized coal particles in said gas, transporting said suspension pneumatically from said vaporizing means to a cyclone separating means through a second conduit means, separating in said cyclone separating means substantially all of said coal particles greater than a predetermined size, withdrawing said separated particles from said cyclone separating means through a third conduit means, introducing said separated coal particles into a mixing means, transporting a second stream of said stabilized slurry from said storage means through a fourth conduit means to said mixing means, mixing said separated coal particles and said second stream of stabilized slurry in said mixing means to provide a coalwater mixture having a predetermined concentration of coal by weight, transporting said mixture from said mixing means to a comminuting means through a fifth conduit, comminuting at least a portion of said coal particles in said mixture to a size less than said predetermined size, transporting pneumatically said coal particles in said suspension and said coal particles in said mixture to a pulverized fuel burner, and burning said coal particles in said pulverized fuel burner.

5. A process for burning the coal particles of a stabilized coal-water slurry in a pulverized fuel burner, said coal particles having a spectrum of sizes and about 70 percent by Weight of said particles having a size which will be retained on a 200 mesh Tyler Standard screen, said stabilized coal-water slurry having a coal concentration of about 60 percent by weight and the remainder water, said process comprising maintaining an inventory of stabilizedslurry in a storage means under substantially quiescent conditions, withdrawing a first stream of said stabilized slurry from said storage means, transporting by pumping through an enclosed conduit said first stream of slurry from said storage means to a vaporizing means, introducing a gas at an elevated temperature into said vaporizing means, vaporizing between 34 to 37 percent by Weight of said stabilized slurry and forming a dispersion of said coal particles in a vapor, transporting said dispersion pneumatically from said vaporizing means to a cyclone separating means through a second conduit means, separating in said cyclone separating means substantially all of said coal particles having a size Which will be retained on a 200 mesh Tyler Standard screen from said dispersion, withdrawing said separated particles from said cyclone separating means through a third conduit means, introducing said separated particles into a mixing means, transporting a second stream of said stabilized slurry from said storage means through a fourth conduit means to said mixing means, mixing said separated coal particles and said second stream of stabilized slurry to form a mixture having about 18 percent water by weight and the remainder coal particles, transporting said mixture from said mixing means to a comminuting means through a fifth conduit, comminuting certain of said coal particles in said mixture so that substantially all of said coal particles will pass through a 200 mesh Tyler Standard screen, transporting pneumatically said dispersion and said mixture to a pulverized fuel burner, and burning said coal particles contained in said dispersion and said mixture in said pulverized fuel burner.

6. A process for burning the different sized coal particles of a stabilized coal-Water slurry in a pulverized fuel burner, certain of said coal particles in said stabilized slurry having a size greater than a predetermined size, said process comprising maintaining an inventory of stabilized slurry in a storage means under substantially quiescent conditions, withdrawing a stream of said stabilized slurry from said storage means, transporting by pumping through an enclosed conduit said stream of slurry from said storage means to a vaporizing means, subjecting said slurry in said vaporizing means to a gas at an elevated temperature to thereby vaporize a portion of said water in said stabilized slurry to form a suspension of said different sized coal particles in said gas containing water vapor, transporting said suspension pneumatically from said vaporizing means to a cyclone separating means through a second conduit means, separating in said cyclone separating means substantially all of said coal particles greater than a predetermined size, withdrawing said separated particles from said cyclone separating means through a third conduit means, transporting said separated coal particles through said third conduit means to a cornminuting means, comminuting at least a portion of said separated coal particles to a size less than said predetermined size, transporting pneumatically said coal particles in said suspension and said separated coal particles to a pulverized fuel burner, and burning said coal particles in said pulverized fuel burner.

7. A process for burning the coal particles of a stabilized coal-Water slurry in a pulverized fuel burner, said coal particles having a spectrum of sizes and about 70 percent by Weight of said particles having a size which will be retained on a 200 mesh Tyler Standard screen, said stabilized coal-water slurry having a coal concentration of about 70 percent by weight and the remainder water, said process comprising maintaining an inventory of stabilized slurry in a storage means under substantially quiescent conditions, withdrawing a stream of said stabilized slurry from said storage means, transporting by pumping through an enclosed conduit said stream of slurry from said storage means to a vaporizing means, introducing a gas at an elevated temperature into said vaporizing means, vaporizing between 23 to 26.5 percent by weight of said stabilized slurry and forming a dispersion of said coal particles in a gas and Water vapor, transporting said dispersion pneumatically from said vaporizing means to a cyclone separating means through a second conduit means, separating in said cyclone separating means substantially all of said coal particles having a size which will be retained on a 200 mesh Tyler Standard screen from said dispersion, withdrawing said sepa- References Cited by the Examiner UNITED STATES PATENTS 333,337 12/1885 Rehmenklau 1l0-106 2,032,402 3/1936 Colby -106 X 2,346,151 4/1944 Burk 241-16 X 2,716,002 8/1955 Craig 110-106 X 2,830,769 5/1958 Work 241--21 X 2,856,872 10/1958 Steinert 110-106 3,019,059 1/ 1962 McMurtrie.

3,073,652 1/ 1963 Reichl 30266 OTHER REFERENCES German patent publication: K 15,217, Aug. 15, 1952.

FREDERICK L. MATTESON, JR. Primary Examiner.

JAMES W. WESTHAVER, Examiner. 

6. A PROCESS FOR BURNING THE DIFFERENT SIZED COAL PARTICLES OF A STABILIZED COAL-WATER SLURRY INA PULVERIZED FUEL BURNER, CERTAIN OF SAID COAL PARTICLES IN SAID STABILIZED SLURRY HAVING A SIZE GREATER THAN A PREDETERMINED SIZE, SAID PROCESS COMPRISING MAINTAINING AN INVENTORY OF STABILIZED SLURRY IN A STORAGE MEANS UNDER SUBSTANTIALLY QUIESCENT CONDITIONS, WITHDRAWING A STREAM OF SAID STABILIZED SLURRY FROM SAID STORAGE MEANS, TRANSPORTING BY PUMPING THROUGH AN ENCLOSED CONCUIT SAID STREAM OF SLURRY FROM SAID STORAGE MEANS TO A VAPORIZING MEANS, SUBJECTING SAID SLURRY IN SAID VAPORIZING MEANS TO A GAS AT AN ELEVATED TEMPERATURE TO THEREBY VAPORIZE A PORTION OF SAID WATER IN SAID STABILIZED SLURRY TO FORM A SUSPENSION OF SAID DIFFERENT SIZED COAL PARTICLES IN SAID GAS CONTAINING WATER VAPOR, TRANSPORTING SAID SUSPENSION PNEUMATICALLY FROM SAID VAPORIZING MEANS TO A CYCLONE SEPARATING MEANS THROUGH A SECOND CONDUIT MEANS, SEPARATING IN SAID CYCLONE SEPARATING MEANS SUBSTANTIALLY ALL OF SAID COAL PARTICLES GREATER THAN A PREDETERMINED SIZE, WITHDRAWING SAID SEPARATED PARTICLES FROM SAID CYCLONE SEPARATING MEANS THROUGH A THIRD CONDUIT MEANS, TRANSPORTING 